Computer Science. PhD vs Masters. What clinches the admit ?

Whats the difference in which the admissions committee of any top
universities look at an MS application and a PhD application ?
does it essentially come down to the applicant's research background,
or does it have any other criteria ? like the SOP or the
recommendation letters ? Is it possible to tailor make an application
to suit the PhD program ? is it possible to make sure that the
committee gets an impression that the applicant is interested in
studying computers ?
Whats the admit statistics for top universites when it comest to
MS/PhD ?
Any other bit of information would helpful....
thanks